Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$206.82	7.553%	$222.4411	$222.44	$222.45	$222.40
Purchase #2	$129.79	5.680%	$137.1621	$137.16	$137.15	$137.20
Purchase #3	$61.71	5.549%	$65.1343	$65.13	$65.15	$65.10
Purchase #4	$190.94	13.160%	$216.0677	$216.07	$216.05	$216.10
Purchase #5	$76.70	11.326%	$85.387	$85.39	$85.40	$85.40
Purchase #6	$43.66	8.151%	$47.2187	$47.22	$47.20	$47.20
Purchase #7	$67.88	12.182%	$76.1491	$76.15	$76.15	$76.10
7 purchase totals =	$777.50		$849.5600	$849.56	$849.55	$849.50